Hot idea: recycling wasted energy

Bill McKibben once lamented the unsexiness of waste heat recovery, an energy efficiency technique that languishes in obscurity despite its potentially huge environmental benefits. Perhaps this story will capture the public imagination: in a move that will save money and cut carbon emissions, the University of Notre Dame in Indiana has begun housing some of its computer servers in the nearby “Arizona Desert Dome,” a conservatory for cacti and other desert plants.

Computer servers create a lot of waste heat — so much so that keeping them cool is a major cost driver and engineering challenge for data centers. Particularly in coal-fired Indiana, air conditioning for data centers equates to a lot of carbon emissions.

Cacti, on the other hand, need a lot of heat, particularly in the winter, when South Bend is blanketed in snow.

You can see where this is going. Housing servers in the desert dome, where air currents can carry away their waste heat, is expected to save the university about $100,000 in cooling costs. Meanwhile, the city will save some of the $70,000 it spends each year to keep the conservatory warm. Given that the conservatory was cut out of the city’s 2010 budget altogether, such steps toward self-sufficiency are necessary to ensure its continued existence.

And here’s some recycled energy news with perhaps wider impact: Vinod Khosla is backing a company that creates solar energy systems designed to harnest the waste heat from traditional solar photovoltaic panels.

Details on the technology are scarce. It sounds a bit like a solar panel smooshed together with a solar water heater — presumably alongside some clever engineering to make the smooshing as efficient as possible. The company claims to be able to double the energy capture of today’s solar photovoltaics, which, if true, would represent an an enormous leap forward for rooftop systems.

Recycled waste heat presents one of the biggest, cheapest opportunities for slashing our carbon budget. It looks like the idea is starting to get its day in the sun.

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